chore: import upstream snapshot with attribution

tests/unit/db/per-engine-analytics.test.ts

@@ -0,0 +1,151 @@
+/**
+ * TDD: getPerEngineAnalytics — per-engine aggregation from compression_analytics.
+ *
+ * DB isolation pattern mirrors tests/unit/db/api-keys.test.ts:
+ * - Temp DATA_DIR, resetDbInstance() before/after, close in test.after().
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+// ─── isolated temp DB ─────────────────────────────────────────────────────────
+
+const TEST_DATA_DIR = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-per-engine-analytics-"));
+const originalDataDir = process.env.DATA_DIR;
+
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const core = await import("../../../src/lib/db/core.ts");
+core.resetDbInstance();
+
+const { insertCompressionAnalyticsRow, getPerEngineAnalytics } =
+  await import("../../../src/lib/db/compressionAnalytics.ts");
+
+// ─── helpers ──────────────────────────────────────────────────────────────────
+
+function resetDb(): void {
+  core.resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+  fs.mkdirSync(TEST_DATA_DIR, { recursive: true });
+}
+
+// ─── lifecycle ────────────────────────────────────────────────────────────────
+
+test.beforeEach(() => {
+  resetDb();
+});
+
+test.after(() => {
+  core.resetDbInstance();
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+  if (originalDataDir === undefined) delete process.env.DATA_DIR;
+  else process.env.DATA_DIR = originalDataDir;
+});
+
+// ─── tests ────────────────────────────────────────────────────────────────────
+
+test("getPerEngineAnalytics returns runs=0 and zeroed metrics for unknown engine", () => {
+  const result = getPerEngineAnalytics("unknown-engine");
+  assert.equal(result.engineId, "unknown-engine");
+  assert.equal(result.runs, 0);
+  assert.equal(result.tokensSaved, 0);
+  assert.equal(result.avgSavingsPercent, 0);
+  assert.equal(result.days, 7);
+});
+
+test("getPerEngineAnalytics returns correct aggregation for headroom rows only", () => {
+  const now = new Date().toISOString();
+
+  // 2 headroom rows: original=1000/compressed=800/saved=200 and original=500/compressed=350/saved=150
+  insertCompressionAnalyticsRow({
+    timestamp: now,
+    mode: "stacked",
+    engine: "headroom",
+    original_tokens: 1000,
+    compressed_tokens: 800,
+    tokens_saved: 200,
+  });
+  insertCompressionAnalyticsRow({
+    timestamp: now,
+    mode: "stacked",
+    engine: "headroom",
+    original_tokens: 500,
+    compressed_tokens: 350,
+    tokens_saved: 150,
+  });
+
+  // 1 caveman row that must NOT appear in headroom results
+  insertCompressionAnalyticsRow({
+    timestamp: now,
+    mode: "stacked",
+    engine: "caveman",
+    original_tokens: 800,
+    compressed_tokens: 600,
+    tokens_saved: 200,
+  });
+
+  const result = getPerEngineAnalytics("headroom");
+
+  assert.equal(result.engineId, "headroom");
+  assert.equal(result.runs, 2, "should count only the 2 headroom rows");
+  assert.equal(result.tokensSaved, 350, "should sum tokens_saved for headroom rows");
+
+  // avgSavingsPercent = round(((1500 - 1150) / 1500) * 1000) / 10
+  //                   = round((350/1500) * 1000) / 10
+  //                   = round(233.33...) / 10
+  //                   = 233 / 10 = 23.3
+  assert.equal(result.avgSavingsPercent, 23.3, `expected 23.3%, got ${result.avgSavingsPercent}`);
+  assert.equal(result.days, 7);
+});
+
+test("getPerEngineAnalytics excludes rows outside the days window", () => {
+  const recent = new Date().toISOString();
+  // 30 days ago — outside the default 7-day window
+  const old = new Date(Date.now() - 30 * 86400_000).toISOString();
+
+  insertCompressionAnalyticsRow({
+    timestamp: recent,
+    mode: "stacked",
+    engine: "headroom",
+    original_tokens: 1000,
+    compressed_tokens: 800,
+    tokens_saved: 200,
+  });
+  insertCompressionAnalyticsRow({
+    timestamp: old,
+    mode: "stacked",
+    engine: "headroom",
+    original_tokens: 2000,
+    compressed_tokens: 1000,
+    tokens_saved: 1000,
+  });
+
+  const result = getPerEngineAnalytics("headroom", 7);
+  assert.equal(result.runs, 1, "should only count the recent row within 7 days");
+  assert.equal(result.tokensSaved, 200);
+});
+
+test("getPerEngineAnalytics falls back to mode column when engine is null (COALESCE behaviour)", () => {
+  const now = new Date().toISOString();
+
+  // Insert a row where engine is explicitly omitted — insertCompressionAnalyticsRow
+  // writes engine = row.engine ?? row.mode, so we cannot get NULL via the helper.
+  // Instead, insert raw via the DB to simulate a pre-engine row.
+  const db = core.getDbInstance();
+  db.prepare(
+    `INSERT INTO compression_analytics (timestamp, mode, engine, original_tokens, compressed_tokens, tokens_saved)
+     VALUES (?, ?, NULL, ?, ?, ?)`
+  ).run(now, "caveman", 600, 400, 200);
+
+  // COALESCE(engine, mode) = 'caveman' for the row above
+  const result = getPerEngineAnalytics("caveman");
+  assert.equal(result.runs, 1, "COALESCE fallback should match engine=NULL, mode=caveman");
+  assert.equal(result.tokensSaved, 200);
+});
+
+test("getPerEngineAnalytics accepts custom days parameter", () => {
+  const result = getPerEngineAnalytics("headroom", 30);
+  assert.equal(result.days, 30);
+});